For those of you who are new atomic swap is the process of swapping coins from one crypto to another without having to go through an exchange. For example, if you want to sell your LTC and buy DASH you will have to get on an exchange, sell LTC for BTC and buy DASH with the BTC you got from LTC sale. Atomic swap makes it possible to exchange coins without having to trade with atomic swap you can directly swap you coins from LTC to DASH. Shapeshift.io also uses atomic swap.